1. Field of the Invention
The present invention relates to a refrigerating device, and more particularly to a refrigerating device for an ammonia refrigerant employing ammonia as a refrigerant.
2. Description of the Related Art
Conventionally, there have been known refrigerating devices which use ammonia gas as a refrigerant, and compressors which compress the ammonia gas. In an ammonia-refrigerant electric compressing device according to Japanese Laid-Open Patent Publication (Kokai) No. H10-112949, in order to insulate respective parts of a motor (such as windings of a stator of the motor), a fluoro resin and the like are used. In the ammonia refrigerant electric compressing device, if the ammonia gas and a lubricant which is insoluble to the ammonia gas are simultaneously used, they are not smoothly circulated in the device. Therefore, as the lubricant, ether oil which is compatible with ammonia is employed. In the device, the lubricant stored at a bottom of the device is pumped up through a rotor shaft of the motor arranged in the vertical direction, and is sprayed by means of gravity from a center hole of the rotor shaft provided at the uppermost portion of the motor to the windings of the stator arranged below. Though the invention is intended to bring the windings of the stator in a state submerged by the lubricant, thereby shutting off a direct contact to ammonia, there is a limitation to deliver the lubricant over the entire windings. Moreover, the structure for storing the lubricant becomes complex, resulting in a large increase in cost. Further, the structure essentially requires an arrangement for vertically standing the motor, resulting in a demerit of restriction on the environment for installation.
In a screw compressor for ammonia according to Japanese Laid-Open Patent Publication (Kokai) No. 2006-118417, though a motor stator and a coil end portion of a motor of the screw compressor are entirely submerged in a oil, a motor rotor rotates at a high speed in the oil with a high viscosity, resulting in a large agitating loss. Consequently, there poses a problem that a required power increases.
Among resins, fluoro resin is especially inactive to most of chemicals, and is considered to have an excellent chemical resistance. However, according to research carried out by the present inventor, even if the fluoro resin providing such excellent chemical resistance is used along with the ammonia gas, and the appearance of the fluoro resin is not damaged, an insulation capability of the motor decreases with the elapse of time.